Conventionally, a food frying machine acting as a liquid heating apparatus for frying foods with edible oil stored in an oil reservoir is disclosed by, for example, Japanese Laid-open Utility Model No. 64837 of 1986. The food frying machine 51 of this type is, as shown in FIG. 11, such that a reservoir portion 54 which accumulates sediment remaining in an oil tank 52 is formed so as to protrude downward from one end side of the bottom 53 of the oil tank 52, a concave heat leading passage 56 which leads heat from a burner 55 is formed so as protrude from the rear side of the bottom 53 of the oil tank 52, and a fin 57 having a cross-shaped section is fixed in the heat leading passage 56.
However, in a food frying machine 51, since a burner 55 is disposed at the upstream side in its lengthwise direction X.sub.7 of a heat leading passage 56 provided at the bottom portion 53 of an oil tank 52, combustion gas resulting from flames of the burner 55 is caused to flow through the heat leading passage 56, wherein although at this time heat efficiency is increased to some degree by the fins 57, the flame of the burner 55 is not positioned downward along the lengthwise direction of the fins 57. Therefore, it is difficult to sufficiently raise the temperature of the fins 57 themselves.
Furthermore, since the heat leading passage 56 formed at the bottom portion 53 of the oil tank 52 is provided so as to have an appointed interval in the direction orthogonal to its lengthwise direction, and the outer circumferential end of the fins 57 is not in contact with the inner surface of the heat leading passage 56 and has an appointed interval, the heat transmitting area enabled by the fins 57 can not be increased. Resultantly, there was such a problem in which sufficient heat efficiency could not be obtained.
Furthermore, since the fins 57 themselves are complicated and are cross-shaped in their sections, the production cost thereof is increased, and since it is necessary to form a concave heat leading passage 56 at the bottom portion 53 of the oil tank 52, the production cost of the oil tank 52 is also increased, and therefore causes a problem in that the structure of the food frying machine 51 itself is complicated and the production cost thereof is accordingly increased.
Furthermore, since the fin 57 having a cross-shaped section is disposed in the heat leading passage 56 in a fixed state, it becomes difficult to eliminate soots or the like which is adhered to the deep side (upward side) of the heat leading passage 56 of the fin 57, wherein cleaning work of the burner portion 55 is made cumbersome, and since the bottom portion 53 of the oil tank 52 is made roughly horizontal, the sediment is deposited on the bottom portion 53, and becomes cumbersome to remove the sediment. That is, there is a problem in that the maintenance of a food frying machine 51 itself is not easily carried out.
The present invention was developed in view of the abovementioned shortcomings and problems, and it is therefore an object of the invention to provide a liquid heating apparatus which is cheap in its production cost with a simplified structure, by which easy maintenance can be carried out and sufficient heat efficiency can be secured.
In order to achieve the abovementioned objects, the invention is featured in that, in a liquid heating apparatus, in which a burner unit is disposed downward of the bottom portion of a liquid tank formed to be a rectangular parallelpiped in its plan view, for raising the temperature of liquid in the liquid tank by heating the bottom portion of the liquid tank using a burner of the burner unit, a heating plane opposite flame ports of the burner and a low temperature portion located downward of the heating plane are formed at the bottom portion of the liquid tank, fins protruding toward the burner direction are juxtaposed and fixed on the rear side of the heating plane in the lengthwise direction thereof, and a fan capable of generating a flow of combustion gas among the fins is provided in the burner unit.
With such a construction, the temperature of liquid accumulated by an appointed amount in a liquid tank is raised by heating the heating plane at the bottom of the liquid tank by combustion of a burner of a burner unit and reaches an appointed temperature level. At this time, the combustion gas generated due to combustion of the burner is caused to forcibly flow through fins secured and fixed on the heating plane in the lengthwise direction of the heating plane by blowing of a fan installed in the burner unit. With a flow of the combustion gas in the fins, the heat transmitting area is expanded to increase heat efficiency, and the fins may be only provided so as to protrude from the heating plane into the burner direction, and the profile thereof is simplified to cause the maintenance thereof to be made easy.
Furthermore, in accordance with another feature of the invention, the burner unit is provided, at one side in the lengthwise direction thereof, with a plurality of rows of flame ports disposed along the lengthwise direction of the fins and a burner having a fan, and is provided with an exhaust portion at the other side in the lengthwise direction thereof. With such a construction, a plurality of rows of flame ports of a burner secured at one side in the lengthwise direction of the burner unit are disposed opposite to and downward of the fins installed on the rear side of the heating plane of the liquid tank, wherein flames coming out from the flame ports heats the heating plane (fins). Accordingly, the combustion gas which has heated the heating plane is caused to flow through the fins, and is exhausted outside from the exhaust portion secured at the other side of the burner unit. Thereby, the combustion gas is caused to efficiently flow through the fins secured on the rear side of the heating plane of the liquid tank, wherein heat efficiency can be further increased.
Furthermore, according to the invention, the burner unit can be provided with a control member, which controls a flow of secondary air, at a point position between the respective flames upward of a plurality of rows of flame ports of the burner. With such a construction, since secondary air regulated by a controlling member is supplied between flames (interior flames) discharged upward from a plurality of rows of flame ports of the burner, the exterior flames are expanded by the secondary air, wherein a stabilized combustion state of the burner can be achieved to cause heat efficiency to be further increased.
In addition, the heating plane of the liquid tank can be formed to be inclined. With such a construction, since sediment, which is apt to be accumulated on the heating plane in the liquid tank, automatically drops and is stored in the low temperature portion by the inclination plane, it becomes simple to eliminate the sediment from the liquid tank, and maintenance can be carried out easier still.
As described above, since fins are fixed on the rear side of the heating plane of a liquid tank and protrude therefrom along the lengthwise direction thereof and a fan for supplying secondary air is provided in the burner unit, combustion gas produced by combustion of the burner of the burner unit is forcibly caused to flow in the lengthwise direction of the heating plane along the fins, whereby sufficient heat efficiency can be obtained.
Still further, since the fins are formed to be channel-like in their cross section and are fixed directly at the rear side of the heating plane of a liquid tank, the construction of the fins and liquid tank can be simplified to cause the production cost of a liquid heating apparatus itself to be decreased. In addition, since the fins are made open in the protruding direction, the cleaning thereof can be simplified, and since sediment which is generated, for example, in a frying operation, can be deposited in a low temperature portion of the liquid tank, it can be easily removed, and it is possible to easily carry out maintenance of a liquid heating apparatus.